1. Field of the Invention
The present invention is directed to a sealed contact device with contact gap adjustment capability, and more particularly to a sealed contact device filled with an arc diminishing gas and having a small adjustable contact gap.
2. Description of the Prior Art
WO 92/17897 discloses a sealed relay or contact device in which a movable contact and associated fixed contacts are disposed within a vacuum chamber. The use of the vacuum chamber enables to reduce a contact gap between the movable contact and the fixed contact in addition to restraining an arc development between the contacts. A demand is frequently seen in the manufacture of the device to adjust the contact gap between the movable and fixed contacts or the amount of an over-travel distance of a plunger carrying the movable contact. For this purpose, a threaded engagement is expected to be used between a plunger carrying the movable contact and an actuator which is driven by an external driving force to move the plunger in the direction of closing the contacts. When modifying the above prior art device with the threaded engagement, it is required to restrict the relative rotation of the plunger and the actuator so that the rotation of the actuator can be translated into a corresponding axial movement of the plunger. Notwithstanding the addition of a structure of restricting the relative rotation of the plunger to the actuator, it is further required that the structure should not interfere with the movement of the movable contact. Therefore, the contact gap adjustment is not easily achieved for the contact device. In addition, a minor rotation of the plunger and the movable contact fixed thereto with respect to the actuator may occur during the assembly of the device. Such minor rotation causes no critical problem in the above prior art device since it utilizes the movable contact in the form of a disk capable of contacting at any peripheral portion with the fixed contacts. However, when the movable contact of a bar-shaped or elongated configuration bridging the fixed contacts is utilized, even the minor rotation of the movable contact with respect to the actuator may lead to misalignment of the movable contact with the fixed contact; thereby, failing to keep a predetermined contacting relation between the movable and fixed contacts.